This invention concerns seals designed to fit pipe or straight threads, and more particularly to seals that provide positive sealing of threads in extreme temperature environments.
Seals for pipe couplings are known from U.S. Pat. Nos.: 3,004,776 (Sebardt); 2,342,425 (Parker); 1,071,585 (Rossell); 2,343,235 (Bashark); 3,009,722 (Augustin); and 3,259,404 (Papenguth). These prior art arrangements use elastomer elements which are not suitable for the extreme temperature environments contemplated by the invention.
Other bushing, ring, and boss type sealing arrangements of the prior art are known from U.S. Pat. Nos.: 2,704,676 (Harding); 3,462,539 (Winston); 3,106,413 (Hamlin); 2,825,584 (Badger et al.); 2,199,647 (Mueller et al); and 3,756,628 (St. Clair).
A pipe or tube coupling device is described in U.S. Pat. No. 3,356,391 in which nuts are formed with an annular packing ring or gland which may be made of deformable metallic or plastic material. This prior art reference does not recognize the critical material requirements for effective thread sealing at the extreme temperature environments contemplated by the invention.
The purpose of the invention is to solve the problem of sealing threads at system pressures up to 3,000 psi and temperatures up to 2,000.degree. F. for 20 minutes, as well as cryogenic (-455.degree. F.) temperatures.